Shellfish allergy – Symptoms & Treatment

Like all other food allergies, allergy to shellfish is yet another abnormal response of the immune system. Although this allergy can develop at any age, it primarily persists in adulthood. This fact makes it stand apart from other food allergies.

Shellfish allergy can also be termed as seafood allergy. People who develop this allergy are intolerant to crab, lobster, shrimp, oysters, scallop, octopus, squid and several other marine animals. Shellfish allergies are unlikely to be outgrown, hence sustain for a lifetime.

What is shellfish allergy?

Shellfish allergy is a type of food allergy where the human immune system overreacts to one or more than one protein present in certain marine organisms. Some people are allergic to all kinds of shellfish whereas some people are allergic to only certain kinds. Proper diagnosis is important to identify and confirm if you are actually suffering from shellfish allergy or to what kind of marine animal you are allergic.

Causes of shellfish allergy

Shellfish being categorized into two broad groups contain different proteins that can cause allergic response in the human body.

The two types of shellfish are:

Crustaceans: Crabs, crayfish, lobster, Prawns and shrimp

Mollusks: Snails, squid, scallops, octopus, oysters and clams

The main cause of shellfish allergy is the malfunctioning of immune system. The immune system identifies certain proteins of shellfish as harmful pathogens instead of recognizing them as harmless.

It then induces the production of antibodies to eliminate them. Every time the body comes in contact with those proteins, the antibodies signal the immune system to release certain chemicals such as histamines. These chemicals are responsible for the onset of allergic signs and symptoms.

Shellfish allergy can be developed without eating it. Inhalation of shellfish smell or handling of shellfish can cause allergic reactions in extremely sensitive people.

Symptoms of shellfish allergy

The onset of symptoms usually takes place within few minutes to hours of having shellfish. The signs and symptoms of shellfish allergy include the following:

  1. Tingling sensation in the mouth
  2. Tingling sensation on lips or surrounding area
  3. Swelling of lips, tongue and throat
  4. Wheezing
  5. Nasal congestion
  6. Trouble breathing
  7. Abdominal cramps
  8. Nausea or vomiting
  9. Diarrhea
  10. Skin hives, swelling, itching, eczema, redness
  11. Dizziness or lightheadedness
  12. Fainting

Shellfish allergy can also cause severe anaphylactic symptoms. They include:

  • Airway constriction
  • Swelling or lump in throat
  • Difficulty to breathe
  • Rapid pulse
  • Shock
  • Severe drop in blood pressure
  • Dizziness or lightheadedness
  • Loss of consciousness

Risk factors

Some possible factors put people at a considerable risk of developing shellfish allergy. We yet cannot prove the role of all of them in developing shellfish allergy, yet they have been put together on the basis of prevalence.

Family history

You are at a higher risk of developing shellfish allergy if shellfish or any other food allergy is common in your family.


Unlike all other food allergies, shellfish allergy is more prevalent in adults. Women commonly suffer from this type of allergy. If it develops in children, boys usually suffer from the same.

Allergies associated with shellfish allergy

Some adverse reactions to seafood resembling shellfish allergy are stated below:

Scromboid fish poisoning

This is an allergy kind of reaction, which occurs after consuming improperly refrigerated fishes. It happens due to the exposure of fish to bacteria. The bacteria break down the fish proteins into histamines that trigger allergic reactions in the human body.

The symptoms and signs of scromboid fish poisoning are quite similar to shellfish allergy symptoms.

Metabisulfite reactions

Preservatives containing metabisulfite are used to prevent prawns from discoloring. This chemical induces allergic reactions in the human body.

Anisakis simplex allergy

This is an allergy to the fish parasite not to the fish. The parasite is heat stable and thus does not get destroyed on cooking.

Treatment of shellfish allergy

The best way to treat shellfish allergy is complete avoidance of shellfish. Despite of the best efforts, it is not always possible to avoid shellfish and you coincidentally happen to come in contact. Doctors prescribe antihistamine medications to treat the initial itchy rashes.

If anaphylaxis occurs, the patient immediately needs to be taken to emergency medical care. Doctors administer injections of epinephrine or adrenaline to bring the fatal life-threatening situation under control. They also advise patients who are at increased risk of anaphylaxis, to carry auto-injectors with them all the time. Sometimes, they also instruct such patients to administer epinephrine right at the first onset of shellfish allergy signs and symptoms and then seek medical help.

Diet and caution

As the situation demands, people prone to shellfish allergy should strictly avoid consuming shellfish. Even if they are only allergic to one class of shellfish, the other class should also be avoided to be on the safer side. People having allergic concerns should try to avoid coming in contact with shellfish, the contact may be of any form, physical contact or inhalation.

It is always advisable to get a formal allergy test done to be sure of your susceptibility to shellfish allergy. Accordingly, you should consult your doctor or dietician what should be your apt diet. If you are an asthma patient, you should try to maintain distance from shellfish. Inhaling the smell might bring disaster to your health. Likewise, an eczema or atopic dermatitis patient should avoid any kind of direct or cross contact with shellfish.

There is a myth that if you are allergic to shellfish, you are also allergic to iodine. You are free to consume iodine; it has absolutely nothing to do with your allergy to shellfish. Glucosamine although derived from shellfish does not pose potential allergy risk, thus can be consumed by people who are allergic to shellfish.

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Dr. Jagdev Singh

Dr. Jagdev Singh is a qualified Ayurvedic Practitioner and Herbalist with B.A.M.S. and M. Sc. in Medicinal Plants. He has a wealth of experience in using Ayurveda to treat patients, including the use of herbal medicine and personalized Ayurvedic diets. His passion for spreading accurate and scientific information about Ayurveda and Medicinal Plants led him to create Ayur Times, a trusted resource for those seeking reliable information on the topic. Through his dedicated work, Dr. Singh has helped thousands of patients find relief and improve their health with Ayurveda and Herbal Medicine.

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